Electrical Question

[Dsull]

Quick question as I'm not 100% knowledgable on 12 volt systems beyond what I read to install my solar, and Automotive systems.

First, the system.
I have the 400 Watt Kit from Renogy. Running 8 AWG between panels to Junction box, and then 4 AWG to controller. 40 AMP breakers on either side of the controller to my buss Bar
2/0 cables to my 4 6-volt batteries
80 amp breaker to Inverter, 300 Amp Catastrophic fuse between battery bank and Bus bar. Inverter running 2/0 Gauge wires to 1000 watt Aims inverter.

Meter is a Victron BMV-712 with 500 Amp shunt. Wired through 2/0 Gauge between bus bar and battery ground.

During the summer I rarely saw it drop below 12.2 volts even with the kids watching movies at night, Mini fridge and my CPAP. Now that it's cold, I'm seeing voltages under load around 11.6-11.7 but the meter only showing about 120 amp hours used. This is with the Furnace running pretty heavy (5-7 amp Draw), a minifridge for the coldies (2-3 amp draw intermittent) and my CPAP going all night (it's a hog, 7-10 amps before I turned down the humidity and heated hose settings to lowest). I got paranoid and ran my little honda 650 generator direct 12 volt to batteries the second night as it charges fastest that way (15 amps output).

I guess my question is should I be scared of the voltage or is it normal with the amount of load hitting the batteries. The meter showed full voltage by around 5 PM after charging around 27 amp hours during the day during full sun, and the tail in and tail out periods as the sun went up and down. Never lost inverter power to A/C system, and furnace was good all night. Just not used to seeing the meter drop that far and throw on low voltage alarm.

Do I need to run 2 more batteries or is this normal?

[PNW Fireguy]

With loads you note running there is a fair draw on your battery bank. I did not see in your post the battery capacity. I am going to assume that based upon your solar kit the bank is modest in capacity. The good news is that your equipment, specifically the lbco, appears to be working correctly. Additional batteries may be just what you need. Don’t forget to use the temp probe and compensation. Ambient temp from weather conditions effect the lead acid charge profiles.

[Dsull]

I have 4 GC-2 Interstates. Based on specs they have a 225 amp hour rating, which is 550 total, which if I understand it gives me 225 usable amp hours, which I'm not reaching overnight. That's what has me not as worried, I just don't know if the loads I'm getting over night will kill them off. Don't want to toast the inverter, and wife does not want to freeze, or have to deal with my chainsaw snoring during the night.

I have enjoyed not having a generator most of the season, but always carry my little guy in the basement as it was nice to have during camping in forest during overcast and solar didn't charge at full rates. I don't mind having to run it once in a blue moon, but if I need to run 6 batteries instead of 4 I'd make the adjustment. Just don't want to spend the money if I don't have to.

I did the exact same setup on my parents trailer, and they haven't had to run their onboard at all other than to run their A/C and Microwave.

[jeffba]

Days are shorter now. Less Sun

[PNW Fireguy]

The furnace and blower are a good load. The added batteries are probably what you need but then it will expose the need for more solar wattage or having to run your generator more. The fall/winter season only exacerbates the issue as well.

[WaltBennett]

Originally Posted by PNW Fireguy

With loads you note running there is a fair draw on your battery bank.

I've had 400 watts of Renogy panels but different other parts (four Trojan T-105's, Morningstar controller and Triminic minitor) for five years now on our Monty and it's worked extremely well. Some suggestions:


Get a Big Buddy or a wall mounted catalytic propane heater, and set it on low when it starts getting cold. Our floor plan won't let me use a wall mount so I use a Big Buddy. If you can't easily hook a heater to your propane, just get a hose and filter, and use a small tank to run it. This will SERIOUSLY cut your furnace cycling down and it uses no DC at all.


My wife has a CPAP as well. Her unit lets her remove the humidifier and she doesn't use the heat function at all. (Maybe she'd want to if the ambient air was really cold?) You should try this and see what you like.


Have you separated all the other current draws off your batteries/inverter? Anything that makes heat is a major one, like an absorption refrigerator (ours is). Keep that on propane. If you've a residential and/or powered cooler, you're in problematic land and probably will have to up your solar game.

[Dsull]

I was running a Mini-fridge, but I'm pulling that out and running ice chests for the coldies. The buddy heater is a great Idea, I'm sure I can tap into the Propane at the Furnace and do a quick coupler, or tap in at the propane bottle area itself to run a coupler in the bedroom.

That would probably take care of the issues as without the furnace I was fine, and during the day I'm bouncing back to full charge before the sun goes down even with all the loads. Thanks!!

[skypilot]

Be careful about not using your furnace - it provides warm air to the under lying things like the black and gray tanks as well as basement.